2.0 Analysis 2.1 Introduction The investigation determined that the Allison 250 C20B engine lost power due to water- contaminated fuel. The analysis will focus on the introduction of water into the helicopter fuel system, and on the subsequent autorotational forced landing. Although improper inspection sheets had been used during a recent 1200-hour inspection, there was no evidence to indicate that this was a factor in the accident. The pilot had not reported a problem with the engine pan drain tube during the 60 hours of flight since the last scheduled inspection, which suggests that the tube had only recently clogged. 2.2 The Introduction of Water into the Fuel System The engine pan overboard drain tube and fuel cell vent tube are easily misidentified where they protrude from the Bell 206B3 fuselage. The tubes are visually similar and are located very close to each other. They are not required to be labelled on the first 3,889 Bell 206 production helicopters. The engine pan drain tube is susceptible to blockage due to the flat routing of the horizontal portion of the tube, the minimal size of the line, and the migration of engine compartment debris. The pilot had the time and facility available to him on fire standby to wash the helicopter and clean the clogged engine pan drain tube. He was familiar with the problem of a blocked drain tube, as evidenced by his habit of carrying a twisted wire to probe the tube. Scratches on the inside wall of the fuel cell vent tube indicate that he may have probed the vent tube when he was clearing the clogged drain tube. It is probable that he also mistakenly back-flushed the fuel cell vent tube, instead of the drain tube, with the available water hose and thereby introduced water into the fuel system. 2.3 The Autorotational Forced Landing The loss of power occurred at low altitude over heavily treed terrain. The proximity of the accident location to an available secondary road and the manoeuvring that was observed by the airborne bird dog crew suggest that the pilot attempted to force land on the road. The low altitude at which the loss of power occurred may have precluded successful autorotation to the site. The pilot's previous experience of a forced landing in a heavily wooded area may have motivated him to attempt to reach the road rather than again autorotate into trees. This most likely resulted in a loss of main rotor autorotational rpm and control, a high rate of descent, and the subsequent overshoot of the intended landing site. 3.0 Conclusions 3.1 Findings The engine lost all power due to water in the fuel. The low altitude at which the loss of power occurred precluded autorotation to a suitable forced landing site. The pilot was observed washing the helicopter and probing in the vicinity of the lower end of the engine pan drain tube with a wire prior to the flight. Laboratory examination identified that the fuel cell vent tube had recently been probed with a wire or a similar instrument. The fuel cell vent tube was not externally identified by label or decal, nor was it required to be by existing regulations. Field reports indicate that the engine pan drain line frequently clogs due to accumulation of bugs, vegetation, and dirt. The helicopter was a Bell 206B3 model; however, Bell 206A/B inspection sheets were utilized for the recent 1200-hour inspection. 3.2 Causes The engine lost power due to water-contaminated fuel. It is probable that the pilot mistakenly introduced water into the fuel system through the fuel cell vent tube when he attempted to back-flush the adjacent engine pan drain tube with a water hose. The low altitude at which the loss of power occurred precluded successful autorotation to a suitable landing site. 4.0 Safety Action 4.1 Action Taken 4.1.1 Operator Action The operator has issued a technical memorandum requiring that all drain lines and vent lines on company Bell 206 helicopters be identified. In addition, the memorandum states that a drain line that is blocked must be removed for cleaning or flushed from the top down to the exit. The memorandum also contains the following warning: UNDER NO CIRCUMSTANCES IS IT PERMISSIBLE TO BACK FLUSH ANY LINE, AS THIS COULD CAUSE CONTAMINATION OF A SYSTEM. 4.1.2 Vent Lines Identification On 09 September 1994, the TSB forwarded an Aviation Safety Advisory to Transport Canada (TC) suggesting that TC require that the fuel vent and engine drain tubes on all Bell 206 helicopters be clearly identified. TC has indicated that a Service Difficulty Advisory will be released to inform operators of the hazards of backflushing vent lines, and recommending that a warning decal be installed near the fuel vent tube outlet. An article on this issue was published in the 4/94 edition of the TC safety publication Maintainer. 4.1.3 Manufacturer Action Bell Helicopter Textron has indicated that a new Technical Bulletin will be released to permit operators of JetRangers with serial numbers prior to 3890 to use the Fuel Cell Vent decal if they so desire. Also, on 19 January 1995, the manufacturer released Operations Safety Notice OSN- GEN-95-26 to all operators of Bell helicopters. This OSN addresses improper washing techniques, and refers operators to appropriate cautions and procedures published in the Bell Helicopter Corrosion Control Guide.